In this work we investigated the effects of an internal O2 impurity on the conductance of elongated gold and silver nanowires (NWs) using density functional theory (DFT) calculations. We found that the O2 interacts with these metallic NWs very differently. In the case of gold NWs, the presence of an internal oxygen molecule locally strengthens the wire, therefore forcing the phase transformations connected to the thinning process (3D to 2D, and 2D to single atom chain) to occur far from the oxygen. As a consequence, towards the end of the elongation the internal O2 is located far from the main conductance channel and therefore has little influence on the conductance of the NW. In contrast, in silver NWs, the presence of an internal oxygen molecule involves a larger charge transfer from the metallic atoms to the oxygen, therefore weakening the Ag-Ag binding. During the initial stages of the elongation, several metallic bonds adjacent to the impurity break, so that in most simulations the NW thinning takes place near the O2. This thinning mechanism places the O2 near the main conductance channel, therefore significantly reducing the conductivity of the elongated silver NWs. For both metals, our findings agree well with published experimental results.
Citation: Journal of Applied Physics
Pub Type: Journals
Nanowire, Conductance, Gold, Silver, Impurity, O2